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Advanced Light Source adds reflection to its repertoire

Tue, 07/12/2011 - 10:42am
ALS_Dome2

As per Energy Secretary Stephen Chu's memo that all new and renovated facilities install a "cool roof", Berkeley Lab's iconic Advanced Light Source dome gets a significant update over its 1940 design.

Paris may have the Eiffel Tower and London has its Big Ben, but Lawrence Berkeley National Laboratory has the iconic domed roof of the Advanced Light Source. Now the ALS is getting a new roof—and not just any roof but a cool roof that will reflect sunlight back into the atmosphere, thus playing a small part in mitigating global warming.

The new roof meets the specifications set out by Secretary of Energy Stephen Chu in a memo last year directing all Department of Energy facilities to install cool roofs when constructing new roofs or replacing old ones at DOE facilities, whenever cost effective over the lifetime of the roof.

Workers will be spending the month of July scrambling up and down the dome, tethered to ropes for safety, pulling out shingles installed more than 20 years ago and putting down new ones. It will take more than five weeks to reroof the 20,000 square foot surface because no more than four workers are allowed on the dome at any one time due to safety requirements.

"This is a major project for the lab," says project manager Ian White. "We're doing things that have never been done before."

While the ALS is less than 20 years old, having been completed in 1993, the dome dates to 1940, when Lab founder and namesake Ernest Orlando Lawrence decided to build a 184-inch cyclotron, an advanced version of his first cyclotron, which later led to his receiving the Nobel Prize in Physics in 1939. The building to house the cyclotron was designed by distinguished architect Arthur Brown, whose works included San Francisco’s City Hall, Opera House, and Coit Tower.

The ALS, a third-generation synchrotron, is an expansion of that original building, with the 90-foot dome kept intact. While it’s known to some Berkeley residents only as the pink building on the hill—visible from miles away in downtown Berkeley—the ALS hosts some 2,000 scientists from around the world every year. They come to use the ALS, including some of the world’s brightest sources of ultraviolet and soft X-ray beams, for researching novel materials, chemical processes, biological structures, and other fields. The beams are shut down and the facility is closed to users during the roofing project.

The other claim to fame of the ALS is its role in the 2003 Ang Lee movie "The Hulk," in which it served as the setting for most of the science scenes. In one climactic sequence, the Hulk rips the Gammasphere (a copy of the real-life gamma-ray detector built at Berkeley Lab, portrayed in the movie as a gamma-ray source) from its connections and hurls it through the roof  of the ALS.

ALS_Dome1

Ernest Orlando Lawrence talks to colleagues at the construction site of the 184-inch cyclotron, built in 1941.

White and his workers have much more mundane matters to deal with, including covering the entire interior of the dome with plastic sheeting in order to collect lead-based paint debris that may fall off during the roofing work, and later scraping the loose paint off before spot resealing. That process required building 30 feet of scaffolding on top of a crane more than 20 feet off the ground that rotates around the dome, following extensive safety precautions to protect workers and equipment. "It's complicated from a safety point of view," White says. "This has never been done at Berkeley Lab."

White brings to the job the friendliness of a Birmingham, Ala. native and the discipline of a Marine veteran who served three tours in Iraq. Still, he confesses that Berkeley Lab's safety policies are more stringent than what he experienced in the military. "I've basically been looking at this project since December," he says. "This is the lab's landmark, so we went through a pretty rigorous process."

For the roof material, White consulted with Berkeley Lab’s cool-roof experts, who have helped devise building standards and work closely with industry to popularize their usage. "When Ian came to us, the first thing I pointed him to was the Cool Roof Rating Council's rated product directory," says Berkeley Lab researcher Haley Gilbert. "You can go in and search the database to find specific roofing products, such as asphalt shingles, and then narrow your results to find the products that comply with the specifications in Dr. Chu’s memo."

The directory includes a roofing product's ratings for three metrics: solar reflectance, thermal emittance, and the "solar reflectance index," or SRI. The SRI is generated from a formula devised at Berkeley Lab and based on a combination of the other two. "Having just one metric makes it easier for building codes and standards and for specifiers to choose and compare products," Gilbert says. "It's used in California’s Title 24, which is the building energy code."

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The interior of the ALS had to be shielded to protect equipment against falling paint chips.

The ALS dome is being re-roofed with Owens Corning Duration Premium Cool Shingles in the "sunrise" color. "Dr. Chu's memo requires an aged solar reflectance index rating of 29," says White. "Ours is 30, so we beat it by one."

The solar reflectance of these shingles is about 25%, says Gilbert, while by comparison, a black asphalt shingle would have a solar reflectance of 5%, trapping heat in the building and releasing heat into the atmosphere and thus contributing to the urban heat island effect.

Another feature of the new roof: while the old shingles were rated for 80 mph winds, the new ones will be able to withstand 130 mph gales. "Eighty miles per hour is theoretically enough for Berkeley, but it doesn’t account for the craziness of the hillside and the dome shape," says Steve Rossi, the ALS Project and Facility Management Group Leader. 

               

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